(a) All dischargers shall comply with the most stringent of the following limitations:
(1) National categorical pretreatment standards as promulgated by the USEPA pursuant to the Act;
(2) State requirements and limitations on discharges to the sewage disposal system;
(3) County supplemental limitations.
(b) When the limits in a categorical pretreatment standard are expressed only in terms of mass of pollutant per unit of production, the Director may convert the limits to equivalent limitations expressed either as mass of pollutant discharged per day or effluent concentration for purposes of calculating effluent limitations applicable to individual dischargers. The Director shall follow conversion requirements established in 40 C.F.R. Section 403.6(C).
(c) When a categorical pretreatment standard is expressed only in terms of pollutant concentrations, an Industrial user may request that the County convert the limits to equivalent mass limits. The determination to convert concentration limits to mass limits is within the discretion of the Director. The County may establish equivalent mass limits only if the industrial user meets all the conditions set forth in subsections (c)(1)A. through (c)(2)D.
(1) To be eligible for equivalent mass limits, the industrial user must:
A. Employ, or demonstrate that it will employ, water conservation methods and technologies that substantially reduce water use during the term of its individual wastewater discharge permit;
B. Currently use control and treatment technologies adequate to achieve compliance with the applicable categorical pretreatment standard, and not have used dilution as a substitute for treatment;
C. Provide sufficient information to establish the facility's actual average daily flow rate for all waste streams, based on data from a continuous effluent flow monitoring device, as well as the facility's long- term average production rate. Both the actual average daily flow rate and the long-term average production rate must be representative of current operating conditions;
D. Not have daily flow rates, production levels, or pollutant levels that vary so significantly that equivalent mass limits are not appropriate to control the discharge; and
E. Have consistently complied with all applicable categorical pretreatment standards during the period prior to the industrial user's request for equivalent mass limits.
(2) An industrial user subject to equivalent mass limits must:
A. Maintain and effectively operate control and treatment technologies adequate to achieve compliance with the equivalent mass limits;
B. Continue to record the facility's flow rates through the use of a continuous effluent flow monitoring device;
C. Continue to record the facility's production rates and notify the Director whenever production rates are expected to vary by more than 20 percent from its baseline production rates determined in subsection (c)(l)C. Upon notification of a revised production rate, the Director will reassess the equivalent mass limit and revise the limit as necessary to reflect changed conditions at the facility; and
D. Continue to employ the same or comparable water conservation methods and technologies as those implemented pursuant to subsection (c)(l )A. so long as it discharges under an equivalent mass limit.
(3) When developing equivalent mass limits, the Director:
A. Will calculate the equivalent mass limit by multiplying the actual average daily flow rate of the regulated process(es) of the industrial user by the concentration-based daily maximum and monthly average limit for the applicable categorical pretreatment standard and the appropriate unit conversion factor;
B. Upon notification of a revised production rate, will reassess the equivalent mass limit and recalculate the limit as necessary to reflect changed conditions at the facility; and
C. May retain the same equivalent mass limit in subsequent individual wastewater discharger permit terms if the industrial user's actual average daily flow rate was reduced solely as a result of the implementation of water conservation methods and technologies, and the actual average daily flow rates used in the original calculation of the equivalent mass limit were not based on the use of dilution as a substitute for treatment pursuant to Section 925.05 of this Chapter. The industrial user must also be in compliance with Section 925.06 of this Chapter regarding the prohibition of bypass.
(d) The Director may grant net/gross allowances to a discharger to adjust for the presence of pollutants in the user's intake water. The user must demonstrate that the control system it proposes or uses to meet applicable categorical pretreatment standards would, if properly installed and operated, meet the standards in the absence of pollutants in the user's water supply. Credit allowance shall be granted only to the extent necessary to meet the applicable categorical pretreatment standards, up to a maximum value equal to the influent value. The granting of the net/gross allowance shall be in accordance with the procedures contained in 40 C.F.R. Section 403.15, as amended.
(e) The County and any user may, by agreement, permit an industrial waste of unusual strength or character to be admitted to the sewage disposal system, either before or after pretreatment, provided there is no impairment of the functioning of the sewage disposal system due to the admission of such wastes and no extra costs are incurred by the County without recompense by the user. A surcharge for extra strength wastewater or wastewater of unusual character shall be determined as provided in Chapter 923 of Part Nine, Title Five of these Ordinances.
(f) As categorical pretreatment standards, the OEPA’s requirements or limits on discharges to sewage disposal systems or the County supplemental limitations are adopted or revised, such adopted or revised limitations shall apply to all users.
(Ord. 2008-375. Adopted 9-29-08.)